US10727039B2ActiveUtilityA1

Mass spectrometer and method for time-of-flight mass spectrometry

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Assignee: THERMO FISHER SCIENT BREMEN GMBHPriority: Jun 20, 2017Filed: Jun 18, 2018Granted: Jul 28, 2020
Est. expiryJun 20, 2037(~10.9 yrs left)· nominal 20-yr term from priority
Inventors:Stewart HamishDmitry GrinfeldAlexander A. Makarov
H01J 49/403H01J 49/405H01J 49/06H01J 49/40H01J 49/406H01J 49/422H01J 49/063
55
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References
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Claims

Abstract

A mass spectrometer comprising: a pulsed ion source for generating pulses of ions having a range of masses; a time-of-flight mass analyzer for receiving and mass analyzing the pulses of ions from the ion source; and an energy controlling electrode assembly located between the pulsed ion source and the time-of-flight mass analyzer configured to receive the pulses of ions from the pulsed ion source and apply a time-dependent potential to the ions thereby to control the energy of the ions depending on their m/z before they reach the time-of-flight mass analyzer. Mass dependent differences in average energy of ions can be reduced for injection into a time-of-flight mass analyzer, which can improve ion transmission and/or instrument resolving power.

Claims

exact text as granted — not AI-modified
The invention claimed is: 
     
       1. A mass spectrometer comprising:
 a pulsed ion source for generating pulses of ions having a range of masses; 
 a time-of-flight mass analyzer for receiving and mass analyzing the pulses of ions from the ion source; and 
 an energy controlling electrode assembly, located between the pulsed ion source and the time-of-flight mass analyzer at an isochronous plane, configured to receive the pulses of ions from the pulsed ion source and apply a time-dependent potential to the ions thereby to control the energy of the ions depending on their m/z before they reach the time-of-flight mass analyzer. 
 
     
     
       2. The mass spectrometer of  claim 1 , wherein the time-dependent potential is synchronised to the arrival times of ions whose energy is to be changed. 
     
     
       3. The mass spectrometer of  claim 2 , wherein the ions whose energy is to be changed are ions at the low mass end of the range of masses. 
     
     
       4. The mass spectrometer of  claim 3 , wherein the time-dependent potential lifts the energy of the ions at the low mass end of the range of masses. 
     
     
       5. The mass spectrometer of  claim 1 , wherein the pulsed ion source comprises an RF ion trap. 
     
     
       6. The mass spectrometer of  claim 1 , wherein the time-of-flight mass analyzer is a multi-reflection time-of-flight mass analyzer having a mass resolving power of at least 30,000. 
     
     
       7. The mass spectrometer of  claim 6 , wherein a total flight path length of the ions is at least 10 metres. 
     
     
       8. The mass spectrometer of  claim 1 , wherein the time-of-flight mass analyzer comprises two ion mirrors opposing each other in a direction X and both mirrors are generally elongated in a drift direction Y, orthogonal to direction X, wherein ions injected into the spectrometer are repeatedly reflected back and forth in the X direction between the mirrors whilst they drift down the Y direction of mirror elongation, the mirrors having a convergence with increasing Y, thereby creating a pseudo-potential gradient along the Y axis that acts as an ion mirror to reverse the ion drift velocity along Y. 
     
     
       9. The mass spectrometer of  claim 1 , wherein the energy controlling electrode assembly is located at a first time focal plane of the ions downstream of the ion source. 
     
     
       10. The mass spectrometer of  claim 1 , wherein the energy controlling electrode assembly comprises a planar electrode oriented in a plane that is substantially orthogonal to the direction of travel of the ions and having an aperture therein through which the ions pass. 
     
     
       11. The mass spectrometer of  claim 1 , further comprising an electrode of lower potential than the pulsed ion source downstream of the energy controlling electrode assembly through which the ions pass. 
     
     
       12. The mass spectrometer of  claim 11 , wherein the electrode of lower potential through which the ions pass is a ground electrode. 
     
     
       13. The mass spectrometer of  claim 1 , wherein the time-dependent potential is a substantially linear voltage ramp. 
     
     
       14. The mass spectrometer of  claim 13 , wherein the magnitude of the voltage ramp is 100-1000V. 
     
     
       15. The mass spectrometer of  claim 13 , wherein a rate of change of the time dependent voltage during the voltage ramp is from 0.1 V/ns to 10 V/ns. 
     
     
       16. The mass spectrometer of  claim 1 , wherein the time-dependent potential is a non-linear voltage ramp. 
     
     
       17. A method of time-of-flight mass spectrometry comprising:
 generating a pulse of ions from a pulsed ion source; 
 receiving and mass analyzing the pulse of ions in a time-of-flight mass analyzer; and 
 using an energy controlling electrode assembly located between the pulsed ion source and the time-of-flight mass analyzer at an isochronous plane to receive the pulses of ions from the pulsed ion source and apply a time-dependent potential to the ions thereby controlling the energy of the ions depending on their m/z before they reach the time-of-flight mass analyzer. 
 
     
     
       18. The method of  claim 17 , wherein the time-dependent potential is synchronised to the arrival times of ions whose energy is to be changed. 
     
     
       19. The method of  claim 18 , wherein the ions whose energy is to be changed are ions at the low mass end of the range of masses. 
     
     
       20. The method of  claim 19 , wherein the ions have a mass-to-charge ratio less than 200. 
     
     
       21. The method of  claim 18 , wherein the time-dependent potential lifts the energy of the ions at the low mass end of the range of masses. 
     
     
       22. The method of  claim 17 , wherein the energy controlling electrode assembly is located in close proximity to the pulsed ion source. 
     
     
       23. The method of  claim 17 , wherein the time-of-flight mass analyzer is a multi-reflection time-of-flight mass analyzer having a mass resolving power of at least 30,000 and a total flight path length of the ions is at least 20 metres. 
     
     
       24. The method of  claim 17 , wherein the energy controlling electrode assembly comprises a planar electrode oriented in a plane that is substantially orthogonal to the direction of travel of the ions and having an aperture therein through which the ions pass. 
     
     
       25. The method of  claim 17 , further comprising an electrode of lower potential then the pulsed ion source downstream of the energy controlling electrode assembly through which the ions pass. 
     
     
       26. The method of  claim 25 , wherein the electrode of lower potential through which the ions pass is a ground electrode. 
     
     
       27. The method of  claim 17 , wherein the time-dependent potential is a substantially linear voltage ramp. 
     
     
       28. The method of  claim 27 , wherein the magnitude of the voltage ramp is 100-1000V. 
     
     
       29. The method of  claim 27 , wherein a rate of change of the time dependent voltage during the voltage ramp is from 0.1 V/ns to 10 V/ns (volts/nanosecond). 
     
     
       30. The method of  claim 17 , wherein the time-dependent potential is a non-linear voltage ramp.

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